| 1. |
- Barenthin, Märta, et al.
(författare)
-
Validation of stability for an induction machine drive using power iterations
- 2005
-
Ingår i: Proceedings of the 16th IFAC World Congress, 2005. - Prague. - 9783902661753 ; , s. 892-897
-
Konferensbidrag (refereegranskat)abstract
- This work is an extension of the paper (Mosskull et al., 2003), in which the modelling, identification and stability of an nonlinear induction machine drive is studied. The validation of the stability margins of the system is refined by an improved estimate of the induced L2 loop gain of the system. This is done with a procedure called power iterations where input sequences suitable for estimating the gain are generated iteratively through experiments on the system. The power iterations result in higher gain estimates compared to the experiments previously presented. This implies that more accurate estimates are obtained as, in general, only lower bounds can be obtained as estimates for the gain. The new gain estimates are well below one, which suggests that the feedback system is stable. The experiments are performed on an industrial hardware/software simulation platform. in this paper we also discuss the power iterations from a more general point of view. The usefulness of the method for gain estimation of nonlinear systems is illustrated through simulation examples. The basic principles of the method are provided.
|
|
| 2. |
- Mosskull, Henrik, et al.
(författare)
-
Adaptive feedforward control of sinusoidal disturbances with applications to electric propulsion systems
- 2024
-
Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661 .- 1873-6939. ; 146
-
Tidskriftsartikel (refereegranskat)abstract
- Generalized adaptive feedforward cancellation with a reference sensor is considered to specifically suppress second harmonic torque oscillations with an ac fed propulsion system for an electric train. A single complex-valued design parameter is tracked through gradient-type adaptation. Both Cartesian and polar parameter representations are considered, resulting in quite varying convergence properties. Three different adaptation algorithms are proposed and evaluated using power lab experiments. At fixed operating conditions, a Cartesian form parameter adaptation is shown to be more robust to the choice of initial conditions, whereas a polar form representation shows better performance when covering a wide range of operating points.
|
|
| 3. |
- Mosskull, Henrik
(författare)
-
Controllability analysis of an inverter fed induction machine
- 2004
-
Ingår i: Proc Am Control Conf. - : IEEE. ; , s. 76-81
-
Konferensbidrag (refereegranskat)abstract
- A controllability analysis of an induction machine fed by a voltage source inverter is performed to gain understanding of fundamental properties of the process from a control point of view. For example the effects of input constraints on reference tracking as well as disturbance rejection are considered and some of the results are verified through simulations.
|
|
| 4. |
- Mosskull, Henrik
(författare)
-
Robust Control of an Induction Motor Drive
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis considers robust control of an induction motor drive, consisting of an input filter, a voltage source inverter and one or several induction motors in parallel. The motor torque is here controlled by using the method Indirect Self Control (ISC), and power oscillations between the inverter and the input filter are damped by means of a stabilization controller in an outer feedback loop. Closed-loop performance with ISC is analyzed under the assumption of a stiff inverter input voltage. It is shown how parameter errors influence the torque loop and the conclusion is that the motor leakage inductance should not be overestimated, especially not with a large desired control bandwidth. It is also shown that model errors enhance cross coupling, but that the performance is quite insensitive even to large parametric errors. Based on the closed-loop model, expressions for the controller parameters are derived to obtain required stability margins. For design of the stabilization controller to suppress oscillations between the inverter and the input filter, it is shown that the effects of time delays and limited torque (or current) control bandwidth are important and cannot be neglected. From models including these non-ideal properties of the control system, explicit expressions for stabilization controllers to use with ISC as well as field-oriented control (FOC) are derived. This is valuable as stabilization often is designed through costly and time-consuming manual tuning. In the controller design, the trade-off between tight torque control and stability of the DC-link is also explicitly considered. In this way reasonable stability margins are obtained, while minimizing the negative effects on torque control. Stability of the closed-loop drive with the proposed stabilization is validated through realistic hardware-in-the-loop simulations using real control HW and SW. Using models obtained from frequency domain system identification, stability of the non-linear closed-loop drive is verified by combining stability results for linear systems with the small gain theorem for the non-linear model errors. This thesis considers the input filter dynamics in connection with torque control of an induction motor. The key result is a model-based framework for simultaneous treatment of DC-link stability and efficient torque control.
|
|
| 5. |
- Mosskull, Henrik
(författare)
-
Some issues on stabilization of an induction machine drive
- 2004
-
Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 0780386825 ; , s. 4441-4446
-
Konferensbidrag (refereegranskat)abstract
- Stability problems due to interaction between the input filter and the voltage source inverter of an induction machine drive are revised. By incorporating properties of the input filter, previous work on stabilization is extended to increase the stability margins of the drive. The strategy is to assure a small phase shift of the inverter input admittance in a frequency region around the input filter resonance frequency. It is motivated why stabilization at zero torque is more critical with a low resonance frequency of the input filter compared to a high. This is a property known from practical experience. It is also shown how dynamic stabilization gains can be used to compensate for limited control bandwidth. This way the drive can be stabilized for very large powers.
|
|
| 6. |
- Mosskull, Henrik
(författare)
-
Stabilization of an induction machine drive
- 2003
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern electric trains almost exclusively use inductionmachines fed by voltage source inverters for propulsion. Toreduce external as well as internal disturbances, an LC-filteris inserted between the input terminals of the drive and theinverter. In connection with efficient torque control of themotors, these filters however potentially make the driveunstable as excitations of the filter resonance are amplifiedby the torque control. The solution to such stability problemsusually is to modify the torque reference according tooscillations in the inverter input voltage. Although thisstrategy may be motivated from simple models of the closed loopdrive, structured tuning of this feed-forward compensation ismore difficult. Experience shows that the compensation must notonly be adapted to the varying dynamics of the drive, but alsoproperties of the torque control and applied inverter pulsepatterns must be considered.This thesis derives an expression for the feedforwardcompensation stabilizing the drive in terms of the operatingconditions. These conditions include the motor speed, operatingpoint torque and flux as well the actual DC-link voltage andtime delays of the torque control. From an equivalent feedbackrepresentation of the drive, the stabilization problem is firstinterpreted as appropriately shaping the inverter inputadmittance. The exact shape of the compensation meeting thedesign requirements is then derived using linear models of thedrive, including control. The derived linear models are alsoused to obtain tuning rules for the torque and flux controllerparameters, given requirements on bandwidth and stabilitymargins. It is assumed that torque is controlled using themethod Indirect Self Control.Stability of the closed-loop drive with the proposedstabilization is validated from measurements. Using modelsobtained from frequency domain system identification, stabilityof the non-linear closed-loop drive is verified by combiningstability results for linear systems with the small gaintheorem for the non-linear model errors.
|
|
| 7. |
- Mosskull, Henrik, et al.
(författare)
-
Stabilization of induction motor drives with poorly damped input filters
- 2007
-
Ingår i: IEEE Transactions on Industrial Electronics. - : IEEE. - 0278-0046 .- 1557-9948. ; 54:5, s. 2724-2734
-
Tidskriftsartikel (refereegranskat)abstract
- Efficient torque control of induction motor drives in combination with resonant dc-link input filters can lead to a type of stability problem that is known as negative impedance instability. An often-proposed solution to this problem is the nonlinear system stabilizing controller (NSSC). Stability is usually analyzed under the simplifying assumption of perfect torque control. This indicates that the NSSC stabilizes the drive at any operating point. In this paper, however, we show power laboratory experiments where the NSSC stabilization fails. An improved framework for stability analysis and synthesis of stabilization, based on a linear. feedback model of the drive, is therefore proposed. With this approach, effects of time delays can easily be included, and stability margins can be directly established from measurements. To solve the indicated problems with NSSC, a stabilization controller that considers the practical limitations of torque control is derived. In the design of the stabilization controller, the tradeoff between damping and acceptable torque control is also explicitly taken into account. The proposed stabilization scheme is implemented and evaluated on a hardware-in-the-loop simulator as well as in a power laboratory. The results show that the proposed method outperforms the NSSC method.
|
|
| 8. |
- Mosskull, Henrik
(författare)
-
μ-Analysis of indirect self control of an induction machine
- 2005
-
Konferensbidrag (refereegranskat)abstract
- Robust stability and performance of an induction machine controlled with Indirect Self Control (ISC) are examined through μanalysis. The analysis indicates poor robust performance at higher rotor speeds. Using reasonable parameter deviations between plant and controller, the predicted bad performance is however hard to verify through simulations. The tested parameter variations seem not to generate the worst case model errors. in simulations, the ISC therefore outperforms linear controllers optimized with respect to the robust performance criterion (at dispense of nominal performance). The large predicted sensitivity to model errors however explains the large impact on performance due to seemingly small differences in the implementation of the ISC control.
|
|
| 9. |
- Wallmark, Oskar, 1976-, et al.
(författare)
-
A robust sensorless control scheme for permanent-magnet motors in railway traction applications
- 2012
-
Ingår i: Electrical Systems for Aircraft, Railway and Ship Propulsion (ESARS), 2012. - : IEEE. - 9781467313704 ; , s. 6387457-
-
Konferensbidrag (refereegranskat)abstract
- Recently, the principle of indirect self control (ISC) has been shown to be suitable also for permanent-magnetmotor drives. In this paper, which is a companion paper to [1], experimental results are presented which show that ISC isa robust and suitable control principle for permanent-magnetsynchronous motors (PMSMs) in railway traction applications, also when the rotor position is not known but estimated. For PMSMs operating with a position sensor, the proposed method enables an improved system reliability if applied as a backup operation mode in the event of a failure of the position sensor.
|
|
